During off hours, trolleys are lined up in rows in Muni's yard on Presidio Avenue, their overhead poles aiming skyward.

Photo: Michael Short, The Chronicle

During off hours, trolleys are lined up in rows in Muni's yard on...

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Muni lines block the sky at the corner of Fillmore and Union streets in picturesque Cow Hollow. The trolleys can get up hills that buses can't manage.

Photo: Michael Short, The Chronicle

Muni lines block the sky at the corner of Fillmore and Union...

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MUNI lines are seen on Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

MUNI lines are seen on Union St. in San Francisco, CA, Friday,...

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MUNI lines are seen on the corner of Steiner and Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

MUNI lines are seen on the corner of Steiner and Union St. in San...

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Busses are seen lined up at the MUNI yard on Presidio Ave. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Busses are seen lined up at the MUNI yard on Presidio Ave. in San...

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Overhead MUNI lines are reflected in a store window on the corner of Fillmore and Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Overhead MUNI lines are reflected in a store window on the corner...

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MUNI lines are seen above a 22 Fillmore bus as it makes it's way down Broadway in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

MUNI lines are seen above a 22 Fillmore bus as it makes it's way...

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Buses are seen lined up at the MUNI yard on Presidio Ave. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Buses are seen lined up at the MUNI yard on Presidio Ave. in San...

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Buses are seen lined up at the MUNI yard on Presidio Ave. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Buses are seen lined up at the MUNI yard on Presidio Ave. in San...

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Workers repair cables that fell down after an incident involving a MUNI bus that injured three pedestrians at Market Street and 5th Street on Monday, June 4, 2012 in San Francisco, Calif.

Photo: Yue Wu, The Chronicle

Workers repair cables that fell down after an incident involving a...

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Overhead MUNI lines are seen on the corner of Fillmore and Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Overhead MUNI lines are seen on the corner of Fillmore and Union...

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Overhead MUNI lines are seen on the corner of Fillmore and Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Overhead MUNI lines are seen on the corner of Fillmore and Union...

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The 24-Divisadero slices through San Francisco's demographics -- starting in Bayview-Hunters Point, one of the city's poorest neighborhoods, and ending in Pacific Heights, one of the wealthiest.

Photo: Carlos Avila Gonzalez, The Chronicle

The 24-Divisadero slices through San Francisco's demographics --...

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A 22 Fillmore bus is seen under MUNI lines on Steiner St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

A 22 Fillmore bus is seen under MUNI lines on Steiner St. in San...

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Overhead MUNI lines are seen on the corner of Fillmore and Union St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

Overhead MUNI lines are seen on the corner of Fillmore and Union...

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A tangle of overhead MUNI lines are seen above a 22 Fillmore bus as it turns onto Steiner St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

A tangle of overhead MUNI lines are seen above a 22 Fillmore bus as...

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MUNI lines are seen on the corner of Broadway and Steiner St. in San Francisco, CA, Friday, December 6, 2013.

Photo: Michael Short, The Chronicle

MUNI lines are seen on the corner of Broadway and Steiner St. in...

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Police officers and a Muni repair crew assess the damage after power lines came down at Parnassus Avenue and Shrader Street in San Francisco, Calif., knocking out power to the neighborhood and disrupting service on the 6-Parnassus and 43-Masonic Muni bus routes on Saturday, March 16, 2013.

Photo: Paul Chinn, The Chronicle

Police officers and a Muni repair crew assess the damage after...

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Naomi Seyfer of Berkeley on a bicycle and a 14 Mission line Muni bus make their way west bound on Mission Street on Monday, February 4, 2013 in San Francisco, Calif.

Photo: Lea Suzuki, The Chronicle

Naomi Seyfer of Berkeley on a bicycle and a 14 Mission line Muni...

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On Fillmore St. in San Francisco, umbrellas mix with overhead Muni wires and raindrops in 2006.

Photo: Katy Raddatz, The Chronicle

On Fillmore St. in San Francisco, umbrellas mix with overhead Muni...

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In this file photo Muni workers on trucks fix the lines on Market Street.

Photo: John Storey, SFC

In this file photo Muni workers on trucks fix the lines on Market...

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Bus-streetcar tie-up on Market St. at 8th Street in January 1971.
A 57-minute noontime power failure that stopped streetcars and trapped buses in the vicinity of Market and Van Ness avenue.

Photo: Joe Rosenthal, The Chronicle

Bus-streetcar tie-up on Market St. at 8th Street in January 1971....

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The Transamerica Pyramid Center is seen from a 30-Stockton Muni bus on Columbus Avenue on Friday, November 30, 2012 in San Francisco, Calif.

Photo: Pete Kiehart, The Chronicle

The Transamerica Pyramid Center is seen from a 30-Stockton Muni bus...

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A Muni bus waits to pick up passengers at Ocean Avenue and Phelan Street in San Francisco, Calif., on Friday, July 30, 2010.

Photo: Paul Chinn, The Chronicle

A Muni bus waits to pick up passengers at Ocean Avenue and Phelan...

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In this file photo a muni bus heads North up Van ness Ave. at California.

The wires that supply power to the buses run above miles of city streets, putting caps of electric lines over some of San Francisco's most traveled intersections before disappearing into rats' nests of overhead wires strung by a motley list of public utilities.

"It's visual pollution," said Anne Brubaker, a founder of the San Francisco Coalition to Underground Utilities. "We're living in what should be one of the most beautiful cities in the world, but you can't see it for all the wires."

Change is coming, albeit slowly, with the improved batteries of the future making it possible for the trolleys to lose their umbilical links to the electric grid. But until then, the people in the antiwire crowd can only grit their teeth and endure.

Necessary evil

"For many people, trolley coaches' quieter, cleaner service outweighs the unsightliness of the overhead wires necessary for their operation," according to a background piece published on the San Francisco Municipal Transportation Agency's website.

"Many" doesn't mean all, however, and the city gets a small amount of regular feedback from residents unhappy with what they consider the eyesore of overhead wires.

"You have to ask whether the visual pollution is more important than the operational advantages of the trolleys," said John Haley, director of transit for the MTA. "For example, it's impossible for buses to get up the grade of California Street."

The trolley system requires environmentalists, along with city officials, to constantly juggle the pluses and minuses. Supervisor Scott Wiener, who has a long-running interest in both Muni operations and the growing proliferation of ugly infrastructure along and above city streets, admits he's ambivalent about the trolleys.

"I'm not a fan of overhead wires," he said. "They're not attractive, they can fall down and they cause problems when it comes to improving the streetscape or widening sidewalks."

And still ...

"I take the 24 (Divisadero) line, and sometimes Muni has to use a regular bus on the route," Weiner said. "There are times when that bus can barely make it up the hills."

Get off and walk

That's not a new problem. The diesel buses on the old 55-Sacramento line were notorious for not always being able to carry a full load of passengers up Nob Hill without having to ask people to get off and walk alongside. The problem ended in 1982, when the far more powerful 1-California trolley took over the route.

Even transit riders unhappy with the snarls of transit wires required by the trolley buses are leery of replacing a system that works.

"The wires are way ugly," said Susan Kwan at she waited for a 22-Fillmore on Union Street. "But what can you do? The bus gets me to work every day."

San Francisco is one of the few cities in the country that still uses electric trolleys, joined by Seattle, Boston, Philadelphia and Dayton, Ohio. Muni's fleet of 311 trolleys (out of about 1,100 total transit vehicles) is the nation's largest.

The number of cities nearly dropped to four a couple of years ago, when a special audit recommended that Seattle scrap its trolleys, tear out the overhead wires and cover the routes with new diesel-electric hybrid vehicles. But complaints from riders, along with a closer look at the financial numbers, convinced the city's transit agency that it made sense to buy new trolleys.

That discussion never came up in San Francisco, which will combine with Seattle to buy new trolley buses for its own fleet. Not only does the trolley's quiet, no-exhaust operation fit the city's efforts to lessen the green footprint of its transportation system, but the electricity for the system also is provided free from the city's Hetch Hetchy power operation.

"There's the visual pollution versus the measurable and real pollution from even the cleanest of diesel vehicles," Haley said. The trolleys "are an integral part of the city, carrying a large percentage of our riders over difficult routes and difficult terrain."

Coming to Van Ness

The trolleys aren't going away, either. On the bus rapid transit route now planned for Van Ness Avenue, "the preference is for electric vehicles," Haley said.

The continuing advance of technology, however, could do what city beautification groups have been unable to accomplish.

"This next group of trolleys could well be the last replacements that will need to use wires," Haley said. "It won't be in the next five years, but in 10 to 12 years we could have the battery technology to move the electric buses off the wire."

Putting on pressure

That day can't come soon enough for groups like San Francisco Beautiful or the various neighborhood organizations that have been pressuring city officials to clear the air above the streets by putting utility lines underground and pay closer attention to what gets attached to the poles that dot the sidewalks.